The invention disclosed herein relates to apparatus for applying labels to containers such as bottles. In particular, the invention pertains to a device for monitoring labels before they are applied to bottles to determine if coded information, such as the date on which the container was filled, has been properly applied by a printing mechanism to the labels.
Labeling machines of the type with which the new monitoring system can be used typically draw labels from a stack of labels in a magazine by means of palettes which oscillate rotationally as they are orbited on a rotor. The oscillating or partially rotating curved palettes move past a glue roller where they acquire a thin film of glue. The palettes then roll over the surface of the foremost labels in the magazine so the labels are picked up by the adhesive force of the glue. The exposed sides of the labels which are uncoated with glue then pass a printing mechanism where coded information is printed on the labels. After the information is printed, the labels, which are still carried on palettes, are rotated into proximity with a gripping cylinder which removes the labels from the palette surfaces and carries them onward to the transport path of the container which is to be labeled.
When there are printing mechanism malfunctions such as the printing mechanism running out of ink, the labels proceed without having the filling date or other coded information printed on them. Bottles from which the filling date are missing are not allowed to be sold under the law of some countries. The seriousness of the problem can be appreciated from realization that modern labeling machines of the type outlined above carry out up to twenty-one labeling operations per second so if there is a printing mechanism defect for only a short time, a substantial economic loss can result.